Certain classes of electrical devices, such as certain types of semiconductor devices, employ one or more conductive, relatively inert layers of material for electrical contacts or electrodes. These relatively inert conductive layers, which are sometimes called barrier layers, prevent impurities or other materials used elsewhere in the device from diffusing, migrating or otherwise moving into or contaminating the active regions of adjacent semiconductor material. Some conductive materials such as aluminum for example can have a deleterious effect if allowed to penetrate into certain semiconductor materials such as various kinds of amorphous semiconductor materials. Two exemplary classes of such electrical semiconductor devices where care must be typically exercised to avoid such problems will now be briefly described.